1. Field of the Invention
The present invention relates to a compound, polymer and film forming composition, more specifically, to an insulating film excellent in film properties such as dielectric constant and mechanical strength and usable for an electronic device and the like.
2. Background Art
In recent years, with the progress of high integration, multifunction and high performance in the field of electronic materials, circuit resistance and capacitance of a capacitor between interconnects have increased and have caused an increase in electric power consumption and delay time. Particularly, the increase in delay time becomes a large factor for reducing the signal speed of devices and generating crosstalk. Reduction of parasitic resistance and parasitic capacitance are therefore required in order to reduce this delay time, thereby attaining speed-up of devices. As one of the concrete measures for reducing this parasitic capacitance, an attempt has been made to cover the periphery of an interconnect with a low dielectric interlayer insulating film. The interlayer insulating film is expected to have superior heat resistance in the thin film formation step when a printed circuit board is manufactured or in post steps such as chip connection and pin attachment and also chemical resistance in the wet process. In addition, a low resistance Cu interconnect has been introduced in recent years instead of an A1 interconnect, and with this tendency, CMP (chemical mechanical polishing) has been employed commonly for planarization of the film surface. Accordingly, an insulating film having high mechanical strength and capable of withstanding this CMP step is required.
As an insulating film having high heat resistance, a polybenzoxazole or polyimide film is widely known. Since it contains an N atom having high polarity, it is not satisfactory from the viewpoints of low dielectric properties, low water absorption, durability and hydrolysis resistance.
Furthermore, organic polymers as described above generally have insufficient solubility in an organic solvent and it becomes an important problem for them to prevent precipitation in the coating solvent or entrapment of particulates in an insulating film. When the polymer main chain is modified to have a folded structure so as to increase the solubility, this disadvantageously causes reduction in both the glass transition point and the heat resistance and it is not easy to satisfy both of these properties at the same time.
Also, a highly heat-resistant resin having a polyarylene ether as the basic main chain is known and it has a relative dielectric constant of from 2.6 to 2.7. In order to realize a high-speed device, however, reduction in the dielectric constant, more specifically, reduction in the relative dielectric constant to preferably 2.6 or less, more preferably 2.5 or less in the form of a bulk without porosification is desired.
An insulating film using a thermal polymer of adamantane substituted with an ethynyl group is disclosed in JP-A-2003-292878 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). However, since this monomer is polymerized without using a polymerization catalyst, it takes long hours to complete the reaction. This results in various problems, for example, an undesirable side reaction such as air oxidation proceeds and causes an increase in the relative dielectric constant of an insulating film thus obtained and by-production of a large amount of a polymer sparingly soluble in a coating solvent worsens the surface condition of the insulating film.